As is generally known, an automotive automatic transmission, which is configured to automatically accomplish upshifting and downshifting, employs a parking-lock mechanism installed in a transmission casing. The parking-lock mechanism is comprised of several internal linkages installed in the transmission casing, namely, a manual shaft, a parking-pawl-actuator rod (simply, a parking rod), a support actuator, and a parking pawl. The manual shaft is configured to rotate in synchronism with movement of a shift lever whose position is selectable by the driver. The parking rod is configured to displace in its longitudinal direction in synchronism with rotary motion of the manual shaft. The support actuator has a sloped face onto which a cam, attached to the tip of the parking rod, runs when a specified longitudinal displacement of the parking rod has been reached. The parking pawl is configured to be forced by the cam when the cam has run onto the sloped face of the support actuator, such that the parking pawl is brought into meshed-engagement with a parking-lock gear (simply, a parking gear) mounted on a transmission output shaft. One such parking-lock-mechanism equipped automatic transmission has been disclosed in Japanese Patent Provisional Publication No. 2007-205383 (hereinafter referred to as “JP2007-205383”). In the automatic transmission disclosed in JP2007-205383, the parking-lock mechanism is accommodated in the transmission casing, which casing includes a transmission case and a converter housing integrally connected to each other to form a housing. Additionally, all of component parts, constructing the parking-lock mechanism, are installed on the transmission case.